Wide-field eyepiece lens system

ABSTRACT

A wide field eyepiece lens system composed, in order from a side of an objective lens system, of a first lens unit which is composed of a plurality of lens elements and has a diverging function, and a second lens unit which is composed of a plurality of lens elements and has a converging function. The eyepiece lens system has an apparent field angle of 75° to 80°, an eye relief of 0.95 f or longer and aberrations favorably corrected over an entire range of a visual field thereof including marginal portions, and is configured so as to satisfy the following conditions (1) and (2): 
     
         -8.0&lt;f.sub.1 /f&lt;-4.8                                       (1) 
    
     
         1.8&lt;D/f&lt;2.6                                                (2)

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an eyepiece lens system which has along eye relief and a wide visual field, and is to be used intelescopes, binocular telescopes and so on.

2. Description of the Prior Art

An eyepiece lens system disclosed by U.S. Pat. No. 1,478,704 is known asa conventional example of eyepiece lens systems which have apparentvisual fields on the order of 70°. Further, an eyepiece lens systemdisclosed by Japanese Patent Kokai Publication No. Hei 6-109,983 isknown as another conventional example of eyepiece lens systems whichhave apparent visual fields on the order of 72° and eye relieves on theorder of 1.3 f (f represents a focal length of an eyepiece lens systemas a whole). Furthermore, an eyepiece lens system disclosed by JapanesePatent Kokai Publication No. Sho 56-85,723 is known as still anotherconventional example of eyepiece lens systems which has apparent visualfields exceeding 80°.

The conventional examples mentioned above have defects which are to bedescribed consecutively below:

The conventional example proposed by the U.S. Pat. No. 1,478,704 has asimple composition which comprises a small number of lens elements, buta short eye relief of 0.6 f to 0.68 f, whereby the eyepiece lens systemwill inevitably has a long focal length when it is configured so as tohave a long eye relief. In addition, this eyepiece lens system has anapparent visual field which is as narrow as 70°.

Further, the eyepiece lens system disclosed by Japanese Patent KokaiPublication No. Hei 6-109,983 has an eye relief of 1.27 f to 1.30 f andis sufficiently compact. However, this eyepiece lens system has anapparent visual field of 72° which is rather narrow or not so muchlarger than those of general wide-field binocular telescopes (havingfield angles of 65° and larger).

Furthermore, the conventional example proposed by Japanese Patent KokaiPublication No. Sho 56-85,723 produces aberrations within a pupilthereof and allows a visual field thereof to be eclipsed.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide an eyepiece lenssystem having an apparent field angle of 75° to 80° which issufficiently wide as compared with those of binocular telescopes, asufficient eye relief having a value of 0.95 f or longer, a pupil withinwhich aberrations are scarcely produced and a visual field within whichaberrations are corrected even on a marginal portion thereof.

The wide-field eyepiece lens system according to the present inventionis composed, in order from an object side of the lens system, of a firstlens unit which consists of, a plurality of lens elements and has adiverging function, and a second lens unit which consists of a pluralityof lens elements and has a converging function; and configured so as tosatisfy the following conditions (1) and (2):

    -8.0<f.sub.1 /f<-4.8                                       (1)

    1.8<D/f<2.6                                                (2)

wherein the reference symbol f represents a focal length of the eyepiecelens system as a whole, the reference symbol f₁ designates a focallength of the first lens unit, and the reference symbol D denotes adistance reserved between the first lens unit and the second lens unit.

In the eyepiece lens system according to the present invention, thefirst lens unit is configured so as to have the diverging function forreducing a Patzval's sum which governs curvature of an image surface.Further, the first lens unit which has the diverging function serves fordirecting marginal rays farther from an optical axis (a springing-upfunction) so that the rays are incident high on the second lens unithaving the converging function. Accordingly, rays emerging from thesecond lens unit are kept high, thereby making it possible to obtain aneyepiece lens system which has a wide visual field and a long eyerelief.

The second lens unit has the converging function, or serves fordirecting the rays which have been spring up by the first lens unit toan eye point while preventing these rays from producing aberrations.

The object of the present invention is attainable by configuring thefirst lens unit and the second lens unit so as to satisfy the conditions(1) and (2) mentioned above.

The condition (1) defines the diverging function of the first lens unit.If the upper limit of -8.0 of the condition (1) is exceeded, the firstlens unit will have a weak diverging power or a low function to springup the marginal rays, thereby making it impossible to obtain asufficient eye relief. If the upper limit of -4.8 of the condition (1)is exceeded, in contrast, the first lens unit will have a strongspringing-up power and the marginal rays will be incident on the secondlens unit at large angles, whereby allowing to obtain a long eye relief,but making it impossible to correct aberrations produced by the secondlens unit, in particular curvature of an image surface which isaggravated at an intermediate image height.

The condition (2) defines a distance to be reserved between the firstlens unit and the second lens unit. If this distance is shorter than thelower limit of 1.8 of the condition (2), the marginal rays will beincident low on the second lens unit, thereby making it impossible toobtain a sufficient eye relief. When an attempt is made to enhance theserays on the second lens unit by shortening the focal length of the firstlens unit, the marginal rays will be incident on the second lens unit atlarge angles and it will be impossible to correct the curvature of theimage surface which is aggravated at the intermediate image height inparticular. If the upper limit of 2.6 of the condition (2) is exceeded,in contrast, the distance between the first lens unit and the secondlens unit will be long enough to obtain the required eye relief, but theeyepiece lens system will have a large total length contrary to theobject of the present invention. When the eyepiece lens system accordingto the present invention is to be used in a binocular telescope whichcomprises a prism or other means for inverting an image in particular,an eyepiece lens system having such a large total length will constitutea cause for enlarging the binocular telescope as a whole.

By selecting compositions which are to be described below for the firstlens unit and the second lens unit, it is possible to configure theeyepiece lens system according to the present invention so as to havefavorable optical performance.

The first lens unit is composed of a cemented lens component whichconsists of a positive lens element and a negative lens element. Thesecond lens unit is composed of a cemented lens component which consistsof a negative lens element and a positive lens element, a positive lenscomponent, and a cemented lens component which consists of a positivelens element and a negative lens element.

The first lens unit has the function to spring up the marginal rays asdescribed above. An amount of lateral chromatic aberration to beproduced is remarkably reduced by composing the first lens unit of apositive lens element and a negative lens element as described above.

The second lens unit has the function to direct the marginal rays, whichhave been sprung up by the first lens unit, to the eye point whilepreventing the rays from producing aberrations. When the cemented lenscomponent which consists of the negative lens element and the positivelens element is disposed on the side of the objective lens system in thesecond lens unit, the positive lens element functions to slightly returnthe marginal rays which have been further sprung up by the negative lenselement after they were sprung up by the first lens unit. Further, acemented surface disposed in the cemented lens component, in particular,produces aberrations of high orders thereby reducing aberrations such asthe curvature of the image surface which is remarkable at marginalportions.

The positive lens component which is disposed in the second lens unithas a function to abruptly deflect the sprung up marginal rays to theeye point. Further, the cemented lens component which is disposed on theside of the observer's eyes, and composed of the positive lens elementand the negative lens element, further deflects the marginal rays whichhave been directed to the eye point by the positive lens component so asto have an apparent field angle of 75° to 80°. Furthermore, the cementedlens component which is disposed on the side of the observer's eyes hasa composition symmetrical with that of the cemented lens component whichis disposed on the side of the objective lens system or is composed, inorder from the side of the objective lens system, of the positive lenselement and the negative lens element so as to cancel aberrationsproduced by the negative lens element and the positive lens element ofthe cemented lens component which is disposed on the side of theobjective lens system.

Moreover, it is desirable to configure the eyepiece lens systemaccording to the present invention so as to satisfy the followingconditions (3), (4), (5) and (6):

    n.sub.2p >1.58                                             (3)

    |υ.sub.1-1 -υ.sub.1-2 |>35 (4)

    0.07<|n.sub.2-11 -n.sub.2-12 |<0.25      (5)

    0.07<|n.sub.2-31 -n.sub.2-32 |<0.25      (6)

wherein the reference symbol n_(2p) represents a refractive index of thepositive lens component disposed in the second lens unit, the referencesymbols n₂₋₁₁ and n₂₋₁₂ designate refractive indices of the negativelens element and the positive lens element respectively used in thecemented lens component disposed on the side of the objective lenssystem in the second lens unit, the reference symbols n₂₋₃₁ and n₂₋₃₂denote refractive indices of the positive lens element and the negativelens element respectively used in the cemented lens component disposedon the side of the observer's eves in the second lens unit, and thereference symbols υ₁₋₁ and υ₁₋₂ represent Abbe's numbers of the positivelens element and the negative lens element respectively used in thefirst lens unit.

The condition (3) defines a refractive index of the positive lenscomponent which is disposed between the cemented lens components in thesecond lens unit. This lens component has the function to abruptlydeflect the marginal rays toward the optical axis so that they aredirected to the eye point. If the lower limit of 1.58 of the condition(3) is exceeded, the positive lens component must have high curvaturefor directing the marginal rays to he eye point, thereby bringing aboutundesirable results such as insufficient marginal thickness of the lenscomponent, spherical aberration produced within a pupil, eclipse of avisual field and/or aggravation of spherical aberration. Further, aPetzval's sum will be enlarged, thereby aggravating curvature of animage surface on marginal portions of the visual field.

For correcting spherical aberration and distortion to be produced withinthe pupil, it is effective to use an aspherical surface on the positivelens component.

The condition (4) is required for configuring the first lens unit so asto be achromatic. If the lower limit of 35 of the condition (4) isexceeded, lateral chromatic aberration will be too remarkable forcorrection by the second lens unit. In particular, a variation(curvature) of lateral chromatic aberration will be largely dependent onimage heights.

The conditions (5) and (6) define differences in refractive indicesbetween the lens elements used in the cemented lens components disposedin the second lens unit. Speaking more concretely, the condition (5)defines a difference in refractive indices between the lens elementsused in-the cemented lens component disposed on the side of theobjective lens system in the second lens unit, whereas the condition (6)defines a difference in refractive indices between the lens elementsused in the cemented lens component disposed on the side of theobserver's eyes in the second lens unit.

If the lower limit of the condition (5) or (6) is exceeded, a cementedsurface disposed in the cemented lens component will have a weakrefractive power, thereby remarkably deforming a meridional imagesurface which is corrected by a difference between refractive indicesbefore and after the cemented surface. If the upper limit of thecondition (5) or (6) is exceeded, in contrast, the positive lens elementused in the cemented lens component has too low a refractive index,thereby enlarging a Petzval's sum of the eyepiece lens system andremarkably curving the image surface at marginal portions of the visualfield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 through FIG. 5 show sectional views illustrating compositions ofa first embodiment through a fifth embodiment of the eyepiece lenssystem according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the eyepiece lens system according to the present invention will bedescribed more detailedly below with reference to the preferredembodiments thereof illustrated in the accompanying drawings and givenin the form of the numerical data which is listed below:

    ______________________________________    Embodiment 1    ______________________________________    β = 7.0, 2ω = 80°, L = 11.0(0.97f), f = 11.371    f.sub.1 = -84.034, f.sub.1 /f = -7.39, D = 27.25, D/f = 2.40    r.sub.1 = 46.229               d.sub.1 = 4.2                           n.sub.1 = 1.51633                                      ν.sub.1 = 64.15    r.sub.2 = -33.692               d.sub.2 = 1.5                           n.sub.2 = 1.62004                                      ν.sub.2 = 36.25    r.sub.3 = -135.478               d.sub.3 = 10.7337    r.sub.4 = ∞               d.sub.4 = 34                           n.sub.3 = 1.56883                                      ν.sub.3 = 56.34    r.sub.5 = ∞               d.sub.5 = 1.5    r.sub.6 = ∞               d.sub.6 = 28                           n.sub.4 = 1.56883                                      ν.sub.4 = 56.34    r.sub.7 = ∞               d.sub.7 = 1.0    r.sub.8 = 30.587               d.sub.8 = 2.9                           n.sub.5 = 1.80518                                      ν.sub.5 = 25.43    r.sub.9 = 84.9748               d.sub.9 = 1.5                           n.sub.6 = 1.51633                                      ν.sub.6 = 64.15    r.sub.10 = 13.8041               d.sub.10 = 27.25    r.sub.11 = -28.0105               d.sub.11 = 2.0                           n.sub.7 = 1.76182                                      ν.sub.7 = 26.52    r.sub.12 = 26.0562               d.sub.12 = 13.5                           n.sub.8 = 1.60311                                      ν.sub.8 = 60.68    r.sub.13 = -20.0185               d.sub.13 = 0.3    r.sub.14 = 41.2073               d.sub.14 = 6.6                           n.sub.9 = 1.7725                                      ν.sub.9 = 49.6    r.sub.15 = -69.3813               d.sub.15 = 0.3    r.sub.16 = 16.2697               d.sub.16 = 9.4                           n.sub.10 = 1.60311                                      ν.sub.10 = 60.68    r.sub.17 = -87.5767               d.sub.17 = 1.84                           n.sub.11 = 1.76182                                      ν.sub.11 = 26.52    r.sub.18 = 30.867    n.sub.2p = 1.7725, |ν.sub.1-1 - ν.sub.1-1`| =    38.7    |n.sub.2-11 - n.sub.2-12 | = 0.15871,    |n.sub.2-31 - n.sub.2-32 | = 0.15871    ______________________________________

    ______________________________________    Embodiment 2    ______________________________________    β = 7.0, 2ω = 80°, L = 11.0(0.97f), f = 11.377    f.sub.1 = -66.466, f.sub.1 /f = -5.84, D = 23.7, D/f = 2.08    r.sub.1 = 46.229                d.sub.1 = 4.2                           n.sub.1 = 1.51633                                       ν.sub.1 = 64.15    r.sub.2 = -33.692                d.sub.2 = 1.5                           n.sub.2 = 1.62004                                       ν.sub.2 = 36.25    r.sub.3 = -135.478                d.sub.3 = 14.24    r.sub.4 = ∞                d.sub.4 = 34                           n.sub.3 = 1.56883                                       ν.sub.3 = 56.34    r.sub.5 = ∞                d.sub.5 = 1.5    r.sub.6 = ∞                d.sub.6 = 28                           n.sub.4 = 1.56883                                       ν.sub.4 = 56.34    r.sub.7 = ∞                d.sub.7 = 1.0    r.sub.8 = 30.5187                d.sub.8 = 2.9                           n.sub.5 = 1.80518                                       ν.sub.5 = 25.43    r.sub.9 = 105.7834                d.sub.9 = 1.5                           n.sub.6 = 1.51633                                       ν.sub.6 = 64.15    r.sub.10 = 12.4262                d.sub.10 = 23.7    r.sub.11 = -37.6462                d.sub.11 = 2.0                           n.sub.7 = 1.76182                                       ν.sub.7 = 26.52    r.sub.12 = 26.4772                d.sub.12 = 13.5                           n.sub.8 = 1.60311                                       ν.sub.8 = 60.68    r.sub.13 = -18.7398                d.sub.13 = 0.3    r.sub.14 = 47.6794                d.sub.14 = 6.3                           n.sub.9 = 1.69680                                       ν.sub.9 = 55.53    r.sub.15 = -91.0670                d.sub.15 = 0.3    r.sub.16 = 15.3289                d.sub.16 = 9.4                           n.sub.10 = 1.60311                                       ν.sub.10 = 60.68    r.sub.17 = -295.2200                d.sub.17 = 1.80                           n.sub.11 = 1.76182                                       ν.sub.11 = 26.52    r.sub.18 = 32.4987    n.sub.2p = 1.6968, |ν.sub.1-1 - ν.sub.1-2 | =    38.7    |n.sub.2-11 - n.sub.2-12 | = 0.15871,    |n.sub.2-31 - n.sub.2-32 | = 0.15871    ______________________________________

    ______________________________________    Embodiment 3    ______________________________________    β = 7.0, 2ω = 75°, L = 11.0(0.97f), f = 11.380    f.sub.1 = -61.427, f.sub.1 /f = -5.40, D = 22.42, D/f = 1.97    r.sub.1 = 46.229                d.sub.1 = 4.2                           n.sub.1 = 1.51633                                       ν.sub.1 = 64.15    r.sub.2 = -33.692                d.sub.2 = 1.5                           n.sub.2 = 1.62004                                       ν.sub.2 = 36.25    r.sub.3 = -135.478                d.sub.3 = 15.52    r.sub.4 = ∞                d.sub.4 = 34                           n.sub.3 = 1.56883                                       ν.sub.3 = 56.34    r.sub.5 = ∞                d.sub.5 = 1.5    r.sub.6 = ∞                d.sub.6 = 28                           n.sub.4 = 1.56883                                       ν.sub.4 = 56.34    r.sub.7 = ∞                d.sub.7 = 1.0    r.sub.8 = 30.8417                d.sub.8 = 2.9                           n.sub.5 = 1.80518                                       ν.sub.5 = 25.43    r.sub.9 = 73.4239                d.sub.9 = 1.5                           n.sub.6 = 1.51633                                       ν.sub.6 = 64.15    r.sub.10 = 12.5142                d.sub.10 = 22.42    r.sub.11 = -43.8831                d.sub.11 = 2.0                           n.sub.7 = 1.76182                                       ν.sub.7 = 26.52    r.sub.12 = 22.4941                d.sub.12 = 13.5                           n.sub.8 = 1.60311                                       ν.sub.8 = 60.68    r.sub.13 = -17.6110                d.sub.13 = 0.3    r.sub.14 = 50.0921                d.sub.14 = 6.0                           n.sub.9 = 1.62041                                       ν.sub.9 = 60.27    r.sub.15 = -103.1101                d.sub.15 = 0.3    r.sub.16 = 14.8691                d.sub.16 = 9.4                           n.sub.10 = 1.60311                                       ν.sub.10 = 60.68    r.sub.17 = -319.7722                d.sub.17 = 1.80                           n.sub.11 = 1.76182                                       ν.sub.11 = 26.52    r.sub.18 = 32.7586    n.sub.2p = 1.62041, |ν.sub.1-1 - ν.sub.1-2 | =    38.7    |n.sub.2-11 - n.sub.2-12 | = 0.15871,    |n.sub.2-31 - n.sub.2-32 | = 0.15871    ______________________________________

    ______________________________________    Embodiment 4    ______________________________________    β = 7.0, 2ω = 80°, L = 11.0(0.97f), f = 11.372    f.sub.1 = -80.450, f.sub.1 /f = -7.07, D = 26.24, D/f = 2.31    r.sub.1 = 46.229               d.sub.1 = 4.2                           n.sub.1 = 1.51633                                      ν.sub.1 = 64.15    r.sub.2 = -33.692               d.sub.2 = 1.5                           n.sub.2 = 1.62004                                      ν.sub.2 = 36.25    r.sub.3 = -135.478               d.sub.3 = 10.3621    r.sub.4 = ∞               d.sub.4 = 34                           n.sub.3 = 1.56883                                      ν.sub.3 = 56.34    r.sub.5 = ∞               d.sub.5 = 1.5    r.sub.6 = ∞               d.sub.6 = 28                           n.sub.4 = 1.56883                                      ν.sub.4 = 56.34    r.sub.7 = ∞               d.sub.7 = 1.0    r.sub.8 = 31.2274               d.sub.8 = 3.8                           n.sub.5 = 1.78472                                      ν.sub.5 = 25.68    r.sub.9 = 99.9764               d.sub.9 = 1.5                           n.sub.6 = 1.51633                                      ν.sub.6 = 64.15    r.sub.10 = 13.6262               d.sub.10 = 26.24    r.sub.11 = -34.5576               d.sub.11 = 2.0                           n.sub.7 = 1.80518                                      ν.sub.7 = 25.43    r.sub.12 = 30.2380               d.sub.12 = 13.0                           n.sub.8 = 1.58913                                      ν.sub.8 = 61.18    r.sub.13 = -19.2241               d.sub.13 = 0.3    r.sub.14 = 42.7299               d.sub.14 = 5.7                           n.sub.9 = 1.77250                                      ν.sub.9 = 49.60    r.sub.15 = -88.3034               d.sub.15 = 0.3    r.sub.16 = 16.7008               d.sub.16 = 9.6                           n.sub.10 = 1.58913                                      ν.sub.10 = 61.18    r.sub.17 = -67.4773               d.sub.17 = 1.90                           n.sub.11 = 1.80518                                      ν.sub.11 = 25.43    r.sub.18 = 59.1871    n.sub.2p = 1.77250, |ν.sub.1-1 - ν.sub.1-2 | =    38.5    |n.sub.2-11 - n.sub.2-12 | = 0.21605,    |n.sub.2-31 - n.sub.2-32 | = 0.21605    ______________________________________

    ______________________________________    Embodiment 5    ______________________________________    β = 7.0, 2ω = 80°, L = 11.0(0.97f), f = 11.372    f.sub.1 = -80.213, f.sub.1 /f = -7.05, D = 26.31, D/f = 2.31    r.sub.1 = 46.229               d.sub.1 = 4.2                           n.sub.1 = 1.51633                                      ν.sub.1 = 64.15    r.sub.2 = -33.692               d.sub.2 = 1.5                           n.sub.2 = 1.62004                                      ν.sub.2 = 36.25    r.sub.3 = -135.478               d.sub.3 = 10.3    r.sub.4 = ∞               d.sub.4 = 34                           n.sub.3 = 1.56883                                      ν.sub.3 = 56.34    r.sub.5 = ∞               d.sub.5 = 1.5    r.sub.6 = ∞               d.sub.6 = 28                           n.sub.4 = 1.56883                                      ν.sub.4 = 56.34    r.sub.7 = ∞               d.sub.7 = 1.0    r.sub.8 = 28.3503               d.sub.8 = 3.8                           n.sub.5 = 1.78472                                      ν.sub.5 = 25.68    r.sub.9 = 54.1429               d.sub.9 = 1.5                           n.sub.6 = 1.51633                                      ν.sub.6 = 64.15    r.sub.10 = 13.3633               d.sub.10 = 26.31    r.sub.11 = -26.3226               d.sub.11 = 2.0                           n.sub.7 = 1.80518                                      ν.sub.7 = 25.43    r.sub.12 = 24.6101               d.sub.12 = 14.0                           n.sub.8 = 1.69680                                      ν.sub.8 = 55.53    r.sub.13 = -21.5812               d.sub.13 = 0.3    r.sub.14 = 39.8383               d.sub.14 = 6.7                           n.sub.9 = 1.77250                                      ν.sub.9 = 49.60    r.sub.15 = -77.3351               d.sub.15 = 0.3    r.sub.16 = 16.1449               d.sub.16 = 9.2                           n.sub.10 = 1.58913                                      ν.sub.10 = 61.18    r.sub.17 = -99.9408               d.sub.17 = 1.89                           n.sub.11 = 1.80518                                      ν.sub.11 = 25.43    r.sub.18 = 34.2909    n.sub.2p = 1.77250, |ν.sub.1-1 - ν.sub.1-2 | =    38.5    |n.sub.2-11 - n.sub.2-12 | = 0.10838,    |n.sub.2-31 - n.sub.2-32 | = 0.21605    ______________________________________

wherein the reference symbols r₁, r₂, . . . represent radii of curvatureon surfaces of respective lens elements, the reference symbols d₁, d₂, .. . designate thicknesses of the respective lens elements and airspacesreserved therebetween, the reference symbols n₁, n₂, . . . denoterefractive indices of the respective lens elements, and the referencesymbols υ₁, υ₂, . . . represent Abbe's number of the respective lenselements. In the numerical data listed above, the reference symbol βrepresents a magnification, the reference symbol 2ω designates anapparent visual field, the reference symbol L denotes a distance asmeasured to an eye point, the reference symbols f represents a focallength of an eyepiece lens system as a whole, the reference symbol f₁designates a focal length of a first lens unit, and the reference symbolD denotes a distance between the first lens unit and a second lens unit.

The first through fifth embodiments have compositions illustrated inFIG. 1 through FIG. 5 respectively, wherein the reference symbols r₁through r₃ represent an objective lens system, the reference symbols r₄through r₇ designate an image inverting prism optical system, and thereference symbols r₈ through r₁₈ correspond to the eyepiece lens systemaccording to the present invention. In FIG. 1 through FIG. 5, thereference symbol r₁₉ represents an eye point and the reference symbold₁₈ designates a distance (L) as measured to an eye point.

Each of the eyepiece lens systems preferred as the embodiments of thepresent invention consists of: a first lens unit which is composed of acemented lens component consisting of a positive lens element and anegative lens element; and a second lens unit which is composed of acemented lens component which consists of a biconcave lens element and abiconvex lens element, and is disposed on the side of the objective lenssystem, a biconvex lens component, and a cemented lens component whichconsists of a biconvex lens element and a biconcave lens element, and isdisposed on the side of the observer's eyes.

As is understood from the foregoing description, the eyepiece lenssystem according to the present invention has an apparent field angle of75° to 80° which is sufficiently large as compared with those ofbinocular telescopes (having field angles of 65° and larger), an eyerelief of 0.95 f and a compact size; nevertheless scarcely allowsaberrations to be produced within a pupil thereof and makes a visualfield almost completely free from aberrations such as curvature of animage surface and, distortion and lateral chromatic aberration over anentire range of a visual field thereof including marginal portionsthereof.

I claim:
 1. A wide-field eyepiece lens system comprising, in order froman object side of the lens system, of a first lens unit which iscomposed of a plurality of lens elements and has a diverging function,and a second lens unit which is composed of a plurality of lens elementsand has a converging function, wherein said eyepiece lens system isconfigured so as to satisfy the following conditions (1) and (2):

    -8.0<f.sub.1 /f<-4.8                                       (1)

    1.8<D/f<2.6                                                (2)

wherein the reference symbol f represents a focal length of saideyepiece lens system as whole, the reference symbol f₁ designates afocal length of said first lens unit, and the reference symbol D denotesa distance between said first lens unit and said second lens unit.
 2. Awide-field eyepiece lens system comprising, in order from an object sideof the lens system, first lens unit which is composed of a plurality oflens element and has a diverging function, and a second lens unit whichis composed of a plurality of lens elements and has a convergingfunction, wherein said first lens unit is composed of a cemented lenscomponent consisting of a positive lens element and a negative lenselement, and wherein said second lens unit is composed of a cementedlens component consisting of a negative lens element and a positive lenselement, a positive lens Component, and a cemented lens componentconsisting of a positive lens element and a negative lens element.
 3. Awide-field eyepiece lens system according to claim 2 satisfying thefollowing conditions (3) through (6):

    n.sub.2p >1.58                                             (3)

    |υ.sub.1-1 -υ.sub.1-2 |>35 (4)

    0.07<|n.sub.2-11 -n.sub.2-12 |<0.25      (5)

    0.07<|n.sub.2-31 n.sub.2-32 |<0.25       (6)

wherein the reference symbol n_(2p) represents a refractive index of thepositive lens component disposed in the second lens unit, the referencesymbols n₂₋₁₁ and n₂₋₁₂ designate refractive indices of the negativelens element and the positive lens element respectively used in thecemented lens component disposed on the side of the objective lenssystem in the second lens unit, the reference symbols n₂₋₃₁ and n₂₋₃₂denote refractive indices of the positive lens element-and the negativelens element respectively used in the cemented lens component disposedon the side of the observer's eyes in the second lens unit, and thereference symbols υ₁₋₁ and υ₁₋₂ represent Abbe's numbers of the positivelens element and the negative lens element respectively used in thefirst lens unit.
 4. A wide-field eyepiece lens system according to claim1, wherein said first lens unit is composed of a cemented lens componentconsisting of a positive lens element and a negative lens element,wherein said second lens unit is composed of a cemented lens componentconsisting of a negative lens element and a positive lens element, apositive lens component, and a cemented lens component consisting of apositive lens element and a negative lens element, and wherein saideyepiece lens system is configured so as to satisfy the followingconditions (3) through (6):

    n.sub.2p >1.58                                             (3)

    |υ.sub.1-1 -υ.sub.1-2 |>35 (4)

    0.07<|n.sub.2-11 -n.sub.2-12 |<0.25      (5)

    0.07<|n.sub.2-31 -n.sub.2-32 |<0.25      (6)

wherein the reference symbol n_(2p) represents a refractive index of thepositive lens component disposed in the second lens unit, the referencesymbols n₂₋₁₁ and n₂₋₁₂ designates refractive indices of the negativelens element and the positive lens element respectively used in thecemented lens component disposed on the side of the objective lenssystem in the second lens unit, the reference symbols n₂₋₃₁ and n₂₋₃₂denote refractive indices of the positive lens element and the negativelens element respectively used in the cemented lens component disposedon the side of the observer's eyes in the second lens unit, and thereference symbols υ₁₋₁ and υ₁₋₂ represent Abbe's numbers of the positivelens element and the negative lens element respectively used in thefirst lens unit.